1. Field of the Invention
The invention relates to an inspection apparatus and an inspection method for detecting particles, flaw, defect, dirt, and the like (hereinbelow, generically called defect) existing in the surface of an object to be inspected such as a semiconductor wafer.
The invention relates to a defect inspection method and a defect inspection apparatus for detecting a defect such as a particle or deformation in a pattern in a manufacturing process of a semiconductor device, a liquid crystal display device, a printed board, or the like.
2. Description of the Related Art
For example, an inspection apparatus for detecting a defect in a semiconductor wafer detects a defect existing in the surface of a wafer by irradiating the surface of the wafer with inspection light such as a laser beam and detecting reflection light or scattered light generated on the surface of the wafer.
In the inspection apparatus of this kind, in the case where a pattern for constructing a chip is formed in the surface of a wafer, usually, an image signal is generated on the basis of the intensity of the detected reflection light or scattered light. An image signal in an inspection area (inspection chip or inspection shot) is compared with an image signal in a reference area (reference chip or reference shot), and a part where the difference between the signals is equal to or larger than a threshold is determined as a particle. As the reference area, an area adjacent to the inspection area (adjacent chip or adjacent shot) or a prepared conforming area (conforming chip or conforming shot) is used.
In the inspection apparatus, inspection condition data corresponding to the kinds of wafers and inspection processes is necessary. It takes long time to generate the data. It takes the longest time for setting a threshold in generation of the inspection condition data.
A threshold is set as follows. First, an inspection is conducted using standard inspection condition data. A detected defect candidate is observed by a microscope, and whether the defect candidate is a defect or a false defect is determined. This work will be called a review hereinbelow. When the number of defect candidates is large, the number of defect candidates to be reviewed and the kinds of defect candidates vary depending on the empirical values of users. Therefore, if a threshold with which all of false defects can be deleted is not found from the defect candidates, even if the threshold is changed and a re-inspection is executed, the false defects cannot be deleted, and the review and the re-inspection are repeated a few times.
Japanese Patent Application Laid-Open (JP-A) No. 2004-177139 describes a method of inputting a result of determination of whether a defect candidate is a defect or a false defect, displaying the defect and the false defect on a defect characteristic quantity distribution display unit, and calculating a change parameter from the distribution result.
In a semiconductor manufacturing process, when a particle exists on a semiconductor substrate (wafer), it causes a defect such as insufficient insulation of a wire or a short-circuit. As a pattern on a semiconductor device is becoming finer, when a small particle exists in the semiconductor substrate, it causes insufficient insulation of a capacitor or defect in gate oxides, etc.
Similarly, also in a liquid crystal display device manufacturing process, when a particle exists on a pattern or a defect occurs in the shape of a pattern, the display device cannot be used. Also in a process of manufacturing a printed board, existence of a particle causes short-circuiting of a pattern and poor connection.
One of conventional techniques for detecting a particle on a substrate is disclosed in JP-A No. 62-89336. In the technique, a semiconductor substrate is irradiated with an s-polarized laser beam, scattered light from a particle generated when a particle is adhered on the semiconductor substrate is detected and compared with an inspection result of the same kind of a semiconductor substrate inspected just before, thereby eliminating a false defect caused by a pattern and enabling a high-sensitive high-reliable particle and defect inspection to be performed.
As the technique of detecting the particle, there is a known method of irradiating a wafer with coherent light, eliminating light emitted from a repetitive pattern on the wafer with a spatial filter, and emphasizing and detecting non-repeated defects and particles.
JP-A No. 1-117024 discloses a particle inspection apparatus for irradiating a circuit pattern formed on a wafer with illumination light in a direction tilted with respect to a main straight line group of the circuit pattern by 45 degrees and preventing diffracted light from the main straight line group from entering the aperture of an objective lens in a detection optical system. In the publication, it is also described that light from straight line groups other than the main straight line group is blocked with a spatial filter.
JP-A Nos. 8-210989 and 2005-337851 describe a method of reducing noise components in an image and improving inspection sensitivity in a non-repetitive pattern portion by dropping coherency of the illumination.
JP-A No. 2000-105203 discloses a conventional technique on an apparatus and method for detecting a defect such as a particle.